Many attempts have been made to identify dietary components that prevent development of breast cancer and/or mammary tumors (MTs). Few studies have produced conclusive findings. However, chronic caloric restriction consistently lowers MT incidence and extends latency in rodents. We find that intermittent restriction/refeeding prevents MT development in transgenic MMTV-TGF-a mice to a greater degree than does chronic restriction, i.e., 3% vs 44% incidence (vs 77% for ad libitum-fed mice). Thus, the manner in which calories are restricted has a major impact on MT development. Hypotheses: 1- The protective effect of intermittent restriction/refeeding is mediated by decreased serum IGF-I and leptin and effects on signaling pathways and/or proliferation/apoptosis; 2-The protective effect of intermittent restriction/refeeding is dependent upon periods of moderately severe caloric restriction and is modified by caloric intake and/or nutrient composition during refeeding; 3- The protective effects of chronic restriction and intermittent restriction/refeeding are dependent upon tumor etiology. In Specific Aim 1 the effect of intermittent restriction/refeeding and chronic restriction on serum IGF-I and leptin in longitudinal and cross-sectional protocols will be assessed. In Specific Aim 2 the effect of intermittent restriction/refeeding and chronic restriction on apoptosis, proliferation, and gene expression of IGF-I and leptin and their receptors in mammary tissue and MTs will be determined. In Specific Aim 3 the effect of serum leptin levels on the protective response of intermittent restriction/refeeding regimen on MT development will be determined. Specific Aim 4 will determine if the protective effect of intermittent caloric restriction/refeeding is dependent upon the MT oncogene and/or background strain of the transgenic mouse. Our long-term objectives are to establish nutrition intervention strategies applicable to humans and/or to provide insights leading to the development of chemopreventive agents to mimic this protective effect. [unreadable] [unreadable]